Assessing CO2 interaction with cement and steel over a two-year injection period: current state and future risks for the MovECBM project in Poland

AbstractOn the site of Kaniow (Poland) a new well was used to inject supercritical CO2 into coal seams over a two year period. The injection was part of an experiment on Enhanced Coal-Bed Methane recovery sponsored by the RECOPOL and MovECBM European project.Part of the interest in ECBM is the possibility to store CO2 in unmineable coal seams for hundreds of years. Safe long-term geological storage, be it in coal or in permeable formations, requires minimizing the risk of CO2 leaking through wells and finding its way back to the atmosphere or to potable aquifers and other permeable formations. Wells are generally recognized as a weak spot in CO2 storage, where containment can break down. This is because cement, steel and elastomers can be corroded by CO2, and the ageing process will be accelerated by any defects in the cement sheath.This paper describes how the long term risk to containment was analyzed by integrating characterization and monitoring measures with lab investigation through a long-term leakage simulator. The conditions of the cement sheath and the tubulars were investigated in detail before and after the CO2 injection period using 3D ultrasonic imaging. The steel corrosion behavior was also extensively investigated and characterized in a lab. All data acquired on the initial state of the well bore and the corrosion behavior of the tubulars was then used to simulate the well evolution with a probabilistic approach, enabling quantification of the containment failure as well as what parts of the well bore were critical for preventing and mitigating leaks